I'd like a DSL to have some parts which relate each other for instance

startInt : 3
endInt : 10
deltaInt: 7

where deltaInt shall always be endInt - startInt

How do you suggest me to modify the editor (i.e. SelectionChangedListener? react on saving, etc) to automatically update the deltaInt if the startInt or endInt is changed or to update the endInt in case the deltaInt is changed?